A pH of a chemical liquid such as a cleaning solution used in a semiconductor process is measured in order to verify a cleaning effect of the chemical liquid. For example, a pH measuring device described in the patent document 1 samples and stores a chemical liquid used in a semiconductor manufacturing process and electrochemically measures a pH value by immersing a measuring electrode in the chemical liquid. The chemical liquid sampled by this measuring device is discarded after the measurement.
However, in accordance with this arrangement, there is a problem that a loss of the chemical liquid increases because the chemical liquid is stored in a measurement container and a considerable amount of the chemical liquid is required to be sampled for measurement.